After four months on the Ranch, it would soon be time for the contestants to say goodbye. At the end of Week 17, the final four would be determined, and they'd be sent home to lose weight on their own for 30 days. It was do-or-die for Filipe, Helen, Mike, Ron, and Tara — and Bob and I didn't let them forget it. Here's how the week went.

How Far They've Come: At the beginning of the week, the players met Alison in the gym, where she stood next to a big TV. It was time for a little trip down memory lane, she explained, and she played footage from the very first day of workouts. None of the players could believe that the huffing, puffing weaklings in that video were actually them. And honestly, they weren't — over 16 weeks, the contestants had all become different people. They were stronger — physically and mentally — than they had ever imagined they would become. To prove it to them, Bob and I recreated their Day 1 workouts, and each player was pumped to realize how much more they could do now. Afterwards, Tara, Helen, and Mike took some time to revel in their progress, each digging their goal outfits out of their luggage to see if they fit yet. And did they ever — Tara rocked her little black dress, Helen was a sexy mama in her skinny jeans, and Mike was a total hottie in his leather jacket. And as if all of this weren't enough to let the players know they'd accomplished something pretty amazing, they paid a visit to Dr. Huizenga to check up on their stats. Adding up all the fat they'd shed, inches they'd lost, and medications they'd tossed aside, Dr. H praised the contestants for going from the sickest group in Biggest Loser history to healthy, inspirational people.

Carrying That Weight All Over Again: This week's challenge was a visit to memory lane as well. As you may remember, the Week 1 challenge involved racing over an enormous hill of sand. Well, imagine that hill times 16, and you have an idea of what this week's challenge looked like. Each player was given a sack filled with the amount of weight they'd lost so far. Carrying the sack, they had to race up and down 16 hills of sand, each representing a different week in the game. As they crested each hill, they got to dump the weight they'd lost in that week and move on. The winner would get a choice — $10,000 or a one-pound advantage at the weigh-in — and the person in second place would get whatever prize the winner didn't choose. Filipe and Mike broke out to take an early lead, while Tara, Helen, and Ron struggled to get over the first hill. It looked like a two-man race until Tara (the machine!) mustered up all her willpower and pushed forward until she overtook them both, winning yet another challenge. Mike came in second, followed by Filipe, Helen, and Ron. The prizes were sweet, but just finishing — and tossing all that weight aside for the last time — was prize enough for everyone.

Turning the Tables: At the end of the week, I showed up at the Ranch thinking I was going to give my players their last-chance beating…and then surprise! It was train-the-trainer day. GREAT. The contestants obviously took a lot of joy in putting Bob and me through the wringer, but we held up just fine…and then we turned around and gave them the beating of their LIVES in their last-chance workout. Hey, it was the least we could do.

Weigh-in and Elimination: The beatings paid off on the scale this week, as everyone put up big losses. Ron dropped 9 pounds, bringing his grand total to 141, while Filipe had a 10-pound loss to bring his total to 130. Helen finally surpassed the 100-pound milestone with her 7-pound loss, and Mike guaranteed himself a spot in the final four by shedding 11 pounds. With an 8-pound loss, Tara also secured a final-four spot — without even needing the 1-pound advantage she'd chosen as her challenge prize. But even with numbers like these, someone had to fall below the yellow line, and this week it was Ron and Filipe. In the elimination room, Mike voted for Filipe to keep his dad in the game, and Helen seconded that vote because she perceived Filipe as the bigger threat. Although he knew the others would be gunning for him, Filipe was disappointed to be taken out of the game, but back at home he's doing great. After an initial plateau, he got back on track and has lost 13 more pounds. Plus, he's inspiring his whole community to eat better and exercise. He even holds a free exercise class in his backyard once a week. How awesome is that?!

Next Week: The final four head home to reunite with their families and try real life on for size. We'll follow them for 30 days and then see them come back to the Ranch for their final weigh-in. It's the last episode before the live Finale, and you don't want to miss it! Be sure to tune in to NBC next Tuesday night!